Optic nerve hypoplasia (including association with septo-optic dysplasia)


What is Optic Nerve Hypoplasia (ONH)?

Optic nerve hypoplasia (ONH) refers to an abnormally small, underdeveloped optic nerve (ON). It is a congenital abnormality, thought to occur in the mid trimester of pregnancy in which a reduced number of axons form the optic nerve.1 The earlier in pregnancy it occurs, the more severe the hypoplasia. It usually affects both nerves (75% of cases) but may be asymmetrical.2

What is the significance of ONH?

ONH is probably the single most common ON anomaly, thought to occur in around 7/100,000 live births.3 It is estimated to account for 12% of childhood blindness in the UK and may be associated with neurological or endocrine abnormalities, particularly septo-optic dysplasia. In bilateral cases, 46% have absence of the corpus callosum or septum pellucidum and 12% have panhypopituitarism. 27% of all children with ONH have endocrine abnormalities, the commonest of which is growth hormone (GH) deficiency.4 Some studies suggest up to 75% have associated CNS abnormality.

Risk factors and associations

Studies of children with ONH have suggested associations with young maternal age, first child, maternal diabetes, prematurity, periventricular leukomalacia and exposure to various toxins during pregnancy (alcohol, anticonvulsants, smoking, SSRIs , and cocaine ) but no firm cause has been established.

It does occur in aniridia , anterior visual system tumours, with some brain malformations (holoprosencephaly, schizencephaly, porencephaly), in septo-optic dysplasia in combination with agenesis of the corpus callosum and/or pituitary insufficiency) and can also be inherited.5

How does ONH present

Optic nerve hypoplasia may present to the ophthalmologist with primary visual problems, or it may be suspected during endocrine or neurological assessment for associated conditions (eg neonatal hypoglycaemia, developmental impairment). Visual presentation depends on severity.

Bilateral/severe ONH

  • Roving eye movements, blindness, sluggish pupil responses.
  • May have see-saw nystagmus in septo-optic dysplasia.
  • Delayed visual maturation.

Mild ONH

  • May be asymptomatic. Nystagmus and/or strabismus may be evident.

Unilateral/asymmetric bilateral

  • Strabismus, unsteady fixation, relative afferent pupillary defect (RAPD).

What are the clinical features that define ONH

The classic ophthalmological feature of ONH is the ‘double-ring’ sign where the true nerve size is represented by the inner ring.

The size of the disc can be estimated by calculating the disc-to-macula (DM) to disc diameter (DD) ratio. If DM/DD is over 3, this is suspicious of ONH, and if it is greater than 4, then ONH is very likely.6

Abnormal disc configurations with reduced nerve fibres can occur with sectoral ONH. The ‘figure 8’ disc is a variant of temporal hypoplasia, it occurs in conjunction with developmental suprasellar tumours. Hypoplasia of the upper part of the optic nerves is seen in children born to mothers with diabetes mellitus.

Ex-premature babies with periventricular leucomalacia (PVL) may show abnormal ON cupping as a variant of optic nerve hypoplasia in normal sized optic discs with reduced axonal numbers. In this case the mechanism is retrograde transynaptic degeneration occurring after 28 weeks.7

MRI features

Children with ophthalmoscopic appearances of ONH have reduced cross-sectional intracranial ON diameters. A cross-sectional area of <2.9mm2 in a child over 12 months of age (by which time the ON has achieved most of its adult size) suggests ONH.8

Visual evoked potentials (VEP)

The VEP can be reduced in severe ONH with reduced acuity. Reduced VEP can be predictive of a poor visual prognosis. The flash ERG is usually normal.9


  1. Taylor D. Optic nerve axons: life and death before birth. Eye 2005;19:499-527
  2. Garcia ML, Ty EB et al. Systemic and ocular findings in 100 patients with optic nerve hypoplasia. Journal of Childhood Neurology 2006;21(11)949-956
  3. Tornqvist K, Ericsson A, Kellen B. Optic nerve hypoplasia: risk factors and epidemiology. Acta Ophthalmol Scand 2002;80:300-304
  4. Siatowski RM, Sanchez JC et al. The clinical, neuroradiographic, and
    endocrinological profile of patients with bilateral optic nerve hypoplasia. Ophthalmology 1997 Mar; 104(3):493-6
  5. Hoyt C. and Taylor D. Pediatric Ophthalmology and Strabismus. Elsevier 2013. ISBN 9781455737819
  6. Dutton GN. Congenital disorders of the optic nerve: excavations and hypoplasia.Eye 2004;18:1038-48
  7. Jacobson L, Hëllstrom A, Flodmark O. Large cups in normal size discs: a variant of optic nerve hypoplasia in children with periventricular leucomalacia. Arch Ophthalmol 1997;115:1263-1269
  8. Birkebaek NH, Patel L et al. Optic nerve size evaluated by magnetic resonance imaging in children with optic nerve hypoplasia, multiple pituitary hormaone deficiency, isolated growth hormone deficiency and idiopathic short stature. J Pediatr 2004;145:536-41
  9. Weiss AH, Kelly JP. Acuity, ophthalmoscopy, and visually evoked potentialsin the prediction of visual outcome in infants with bilateral optic nerve hypoplasia. J AAPOS 2003 Apr;7(2):108-115
  10. Mehta A, HindmarshPC et al . Congenital hypopituitarism : clinical ,molecular and neuroradiological correlates. Clin. Endocrinol 2009;71:376-382
  11. Deal C, Hasselmann Cet al. Associations between pituitary imaging abnormalities and clinical and biochemical phenotypes in children with congenital growth hormone deficiency : data from an international observational study. Horm Res 2013;79:283-292
  12. Chen SC, McDevitt H et al . Early Identification of Pituitary Dysfunction in Congenital Nasal Pyriform Aperture Stenosis : recommendations Based on Experience in a Single Centre. Horm Res Paediatr 2015 ; 83 : 302 -310)


Diagnostic and investigative pathway

flowchart to be inserted here 

Editorial Information

Last reviewed: 01/05/2022

Next review date: 01/05/2025

Author(s): Clinical Guidelines Subgroup.

Version: V2

Author email(s): nss.speg@nhs.scot.

Approved By: SPEG Guidelines Group, SPEG Steering Group

Document Id: NSD610-021.07